ISSN:
1434-0879
Keywords:
[3H]Tamsulosin
;
Radioreceptor assay
;
Human prostates
;
α1-antagonists
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract The binding of a novel radioligand, [3H]tamsulosin, to human prostatic membranes with benign prostatic hypertrophy (BPH) has been characterized. [3H]Tamsulosin rapidly associated with its binding sites in human prostatic membranes with BPH, and the binding reached steady state by 30 min at 25°C. The rate constants for association and dissociation of [3H]tamsulosin binding were calculated to be 0.21±0.05/nM per minute and 0.01±0.004/min, respectively. The specific binding of [3H]tamsulosin in human prostatic membranes was saturable and of high affinity (K d=0.04±0.01 nM). The density of [3H]tamsulosin-binding sites (B max) was 409±28 fmol/mg protein. The K d and B max values for [3H]tamsulosin binding in human prostates were significantly lower than those for [3H]prazosin binding. [3H]tamsulosin binding was remarkable for its significantly lower degree of nonspecific binding. Six α-adrenoceptor antagonists competed with [3H]tamsulosin for the binding sites in the rank order: tamsulosin〉WB4101〉prazosin〉S-(+)-isomer〉naftopidil〉yohimbine. The binding affinities (pKi) of these antagonists for [3H]tamsulosin binding in human prostates closely correlated with their pharmacological potencies (pA2) in prostates. In conclusion, [3H]tamsulosin selectively labels α1-adrenoceptors in human prostates, and thus may become a useful radioligand for the further analysis of these receptors.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00297194
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